Three-point hitches are used at the rear and at the front of work vehicles to lift, carry, push and pull various implements. Three-point hitches typically include a rocker or rocker shaft, lift links, lower or draft links, an upper or center link and rocker shaft actuators. The rocker shaft is pivotably supported by the work vehicle and includes links pivotably connected to the lift links.
The rocker shaft provides synchronized lifting of the draft links and sums the lift forces of the hydraulic lift cylinders to maintain the implement in a stable roll axis while in use or at rest. The lift links extend from the arms of the rocker shaft and are pivotably connected to the draft links. The draft links are themselves pivotably connected to the work vehicle. The actuators are pivotably coupled at one end to the work vehicle and at an opposite end to the rocker shaft to pivotably raise and lower the rocker arms. Because the arms of the rocker shaft are coupled to the lift links and thereby to the draft links, such pivotal raising and lowering of the rocker shaft arms correspondingly pivotably raises and lowers the draft links to thereby lift and lower implements mounted on the draft links.
To attach the three-point hitch to a three-point hitch implement, it is necessary to align the draft links with corresponding attachment points on the implement. However, the attachment points on the three-point hitch implement are frequently out of alignment due to the implement being parked on uneven ground or on soft ground which allows the implement to repose into an unlevel misaligned condition. As a result, the operator must realign the draft links with the attachment points of the implement.
To enable the draft links to be realigned with the attachment points of the implement, conventional lift links include mechanical length adjustment features such as turn buckles. These turn buckles enable the operator to vary the length of the lift links so as to align the end of the lift links with the attachment points of the implement.
Although commonly used in both front and rear mounted three-point hitches, the use of such turn buckles to adjust the length of the lift links and to thereby align the draft links with the implement attachment points has several drawbacks. First, adjusting such turn buckles requires that the operator stop and exit the work vehicle to access the turn buckles at the rear of the work vehicle. Second, adjustment of the turn buckles is often extremely difficult and requires additional tools. Because turn buckles typically include threaded parts, the threaded parts frequently accumulate dust, rust or other contaminants upon them making adjustment of the turn buckle difficult.
Furthermore, adjustment of the lift links, once attached to the implement, is also inconvenient and time consuming. In many situations, it is also necessary to level the draft links once they are attached to the implement due to the large loads placed upon the lift links. As a result, the operator frequently must lower the implement to reduce loads upon the lift link in order to manually adjust the turn buckle and the length of the lift link. Consequently, the operator must climb into and out of the work vehicle multiple times.
Thus, there is a continuing need for a draft link adjustment mechanism which provides for easy and inexpensive adjustment of draft links for attachment to an implement and leveling of the draft links after attachment to an implement.